In a conventional vehicle power unit, scavenger pumps are disposed on the left and right sides of the mating plane of a horizontally split crankcase, and the scavenger pumps are arranged in a dual array, resulting in a complex structure. Furthermore, a feed pump and a lubricant oil filter are provided to bulge to one side from the split plane of the crankcase, so that the crankcase is increased in size, and so is the power unit in its entirety.